Republican US Senator Scott Brown questioned Democratic challenger Elizabeth Warren’s claim of Native American heritage in the opening moments of a lively high-stakes television debate tonight.

When moderator Jon Keller asked if character was an issue in the race, Brown answered, “I think character is important. ... Professor Warren claimed she was a Native American, a person of color. And as you can see, she’s not.”

“This is my family, this is who I am, and it’s not going to change,” said Warren.

The candidates, standing at lecterns in the studios of WBZ-TV, also jousted on a variety of other issues, including women’s pay, energy policy, and abortion.

Brown charged Warren with wanting to raise taxes and with misrepresenting his views.

“I’m on the taxpayer’s side,” he said, asserting that Warren was “obsessed with raising taxes.”

Warren, who repeatedly cited Brown’s votes on various issues in the Senate and charged him with using “madeup numbers,” shot back that Brown was trying to “protect the big guys” and siding with “millionaires and billionaires.”

“I want to go to Washington to fight for working families,” she said.

The Globe reported Sunday that questions about Warren’s roots have dogged her campaign since the story broke in April. Warren, a Harvard Law professor, has acknowledged that she had identified herself as a minority in a legal directory for nearly a decade, and she was listed as a Native American in federal forms filed by Harvard and the University of Pennsylvania where she worked. But she has said her heritage claim played no role in her career advancement.

The Globe story reported that some members of Warren’s extended family had also heard stories of Native American blood in the family, but others had not.

Brown challenged Warren to release her personnel records to prove that her claim of Native American heritage had played no role in her getting jobs.

“You refuse to release your records, and I think that speaks volumes,” he said.

Warren pointed to the fact that Professor Charles Fried, former solicitor general in the Reagan administration, who sat on the committee that recruited Warren for her Harvard job, has said that he was unaware of her ancestry when she was hired.

“There’s nothing else there. The question has been asked and answered. I think the senator just doesn’t like the answer,” Warren said.

Warren and Brown also tangled over Brown’s recent statement that he would vote against a plan to extend Bush era tax cuts, if the cuts were not extended for those earning over $250,000 a year.

“He would let taxes go up for 98 percent of families in order to protect tax breaks for the top 2 percent,” said Warren, who is known for her talent for clearly articulating complicated issues. “I’ll make it crystal clear. I will not vote to increase taxes on working families, not ever.”

Brown said the US Chamber of Commerce had said that Warren’s tax policies were the “greatest threat to free enterprise.”

“We already have a tremendous amount of tax revenue in Washington right now. ... I’m not going to raise taxes on our job creators,” he said.

Warren also raised questions about Brown’s endorsement by “antichoice groups;” his vote against a bill that would have expanded the rights of working women to challenge discrimination; and his cosponsoring of the Blunt Amendment, which would allow health plans and employers to refuse to pay for contraception and other medical services if they have a religious or moral objection.

“You should stop scaring women,” Brown retorted.

“I’ve been fighting for women for a long, long time,” he said. “Listen, we’re both pro-choice. I’m a moderate pro-choice Republican. I always have been.”

Warren said the race “may really be for control of the Senate,” saying that Brown would vote with Republicans in Washington.

But Brown said he was the “second most bipartisan senator” in Washington, referring to a 2011 Congressional Quarterly study that gave him that ranking and to a recent Washingtonian magazine article that declared him the “least partisan senator.”

While Warren said the race was about the issues and seemed determined to focus on Brown’s votes in Washington, Brown took some more personal potshots, at one point criticizing Warren, who has a sizeable income, for not using a feature of the Massachusetts tax form that allows people to give more to the state than is required by their taxes.

At another point, during a discussion of higher education reform, he referred to the income earned by Warren and her husband and suggested that it was “no wonder costs are high” at colleges.

A drama played out even before the debate began, when Brown raised the possibility he might miss the event because of the Senate’s voting schedule. Democratic leaders challenged that assertion. Brown eventually rushed to the airport to catch a flight to Boston, making it to the TV station with about 40 minutes to spare — arriving in his trademark green pickup.

The debate, moderated by Jon Keller, WBZ-TV political analyst, came as the two candidates appeared to be running a close race. Warren has had a small lead in four recent polls, while a fifth gave the lead to Brown.

A total of four debates are slated in the race, which is being closely watched nationally. The other debates are Oct. 1 in Lowell, Oct. 10 in Springfield, and Oct. 30 in Boston.

The telegenic Brown was a little-known Republican state senator from the town of Wrentham until he won a surprise victory against Attorney General Martha Coakley in the January 2010 special election. The election was needed to fill the seat left vacant by the death of long-time Democratic US Senator Edward M. Kennedy.

While he appeared to have been lifted by the Tea Party fervor that would later roil the November 2010 elections, Brown has tried to project an image of being an independent thinker as he represents the traditionally Democratic state in Washington.

Warren entered the race about a year ago and was instantly seen as the Democratic frontrunner, considered a formidable candidate with intellectual firepower and a ringing populist-tinged message. She was known for her criticism of the financial industry, which she has accused of carrying out predatory practices. Her work in Washington included setting up a new consumer protection agency.